Third cylinder low compression.

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mentalQtip
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Third cylinder low compression.

Post by mentalQtip » Sat Apr 09, 2016 6:49 pm

'77 bus with fuel injected two liter. Has hydraulic valves.

This bus has a history of poor starting ever since I installed this engine.
Doesn't want to idle well and has no zip at all.
Compression: 150 125 90 140. The 90 went up to 110+ when I squirted oil in.
This bus has new rings. The added oil suggests a ring problem. Would this be an indication that I need to pull the engine and remove the 3/4 head and try to see whats what?
I'm frustrated with trying to get this bus into a reliable driver and take my wife camping.

Thanks

Joseph

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energyturtle
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Re: Third cylinder low compression.

Post by energyturtle » Sun Apr 10, 2016 7:24 am

I would start with another valve adjustment before I panic. When I was first learning how to adjust hydros, i found that if I adjusted the valves cold, and followed the 1 1/2 turns past 0 lash, my bus did not run well, and my compression fluctuated by 20-30 psi. When I adjusted them warm to 1/4 turn past 0 lash, my compression was 130-135 on all 4, and my bus had the "zip" you are referring to. Also, did you break in the rings properly? Were the rings staggered properly, away from the wrist pin on installation?
Scottie

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Amskeptic
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Re: Third cylinder low compression.

Post by Amskeptic » Sun Apr 10, 2016 7:48 am

mentalQtip wrote:'77 bus with fuel injected two liter. Has hydraulic valves.

This bus has a history of poor starting ever since I installed this engine.
Doesn't want to idle well and has no zip at all.
Compression: 150 125 90 140. The 90 went up to 110+ when I squirted oil in.
This bus has new rings. The added oil suggests a ring problem. Would this be an indication that I need to pull the engine and remove the 3/4 head and try to see whats what?
I'm frustrated with trying to get this bus into a reliable driver and take my wife camping.

Thanks

Joseph

Looking at your compression readings, I see that the right side of the engine has unusually high compression. I think this engine may not have matched deck heights or combustion chamber volumes. This is a strike against the engine as far as reliable highway driving.

Do your basic homework! Correct valve adjustments, dwell, timing, correct mixture at operating temps, idle speed at 1,000. Poor starting? Check for fully open auxiliary air regulator, no cracked elbows or hoses anywhere.
Check brake booster circuit. It has to hold vacuum. You could have a split brake booster hose under the left frame rail and it would torment your engine with inexplicable crap running . . . :blackeye:
Colin
BobD - 1978 Bus . . . . . . . . . . . 111,155 miles
Chloe - 1970 bus . . . . . . . . . . . 206,820 miles
Naranja - 1977 Westfalia . . . . . 108,000 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 1991 Lexus LS400 . . . 78,885 miles

mentalQtip
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Re: Third cylinder low compression.

Post by mentalQtip » Sun Apr 10, 2016 3:25 pm

Regarding the rings, I did set them properly compared to the wrist pins but never could really break them in properly because I couldn't get the bus to run well enough to really take it on the road.
I'm going to try changing the valve settings and go from there. I can't get the idle to increase at all. Mixture would be a new one to adjust for me.

Thanks

Joseph

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Amskeptic
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Re: Third cylinder low compression.

Post by Amskeptic » Tue Apr 12, 2016 2:50 pm

mentalQtip wrote:Regarding the rings, I did set them properly compared to the wrist pins but never could really break them in properly because I couldn't get the bus to run well enough to really take it on the road.
I'm going to try changing the valve settings and go from there. I can't get the idle to increase at all. Mixture would be a new one to adjust for me.

Thanks

Joseph
Think about a visit when I am in town.
( I like my coffee black. :bom: )

Colin
BobD - 1978 Bus . . . . . . . . . . . 111,155 miles
Chloe - 1970 bus . . . . . . . . . . . 206,820 miles
Naranja - 1977 Westfalia . . . . . 108,000 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 1991 Lexus LS400 . . . 78,885 miles

mentalQtip
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Re: Third cylinder low compression.

Post by mentalQtip » Wed Apr 13, 2016 5:46 pm

Just adjusted the valves warm 1/4 turn past zero lash and fired it up(after I went back to replace the distributor cap). Sounded different. I backed it out and WOW. The engine was so much quieter, pulled smoother with more life, idled much better, and the exhaust was soooooo quiet and smooth. Night and day.
Not perfect. Still idles up and down but just a little now, and I think it still could be stronger but I am happy for now.

Yay!

Thanks

Joseph

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Amskeptic
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Re: Third cylinder low compression.

Post by Amskeptic » Thu Apr 14, 2016 10:48 am

mentalQtip wrote:Just adjusted the valves warm 1/4 turn past zero lash and fired it up(after I went back to replace the distributor cap). Sounded different. I backed it out and WOW. The engine was so much quieter, pulled smoother with more life, idled much better, and the exhaust was soooooo quiet and smooth. Night and day.
Not perfect. Still idles up and down but just a little now, and I think it still could be stronger but I am happy for now.

Yay!

Thanks

Joseph
Good. Ready for the road? See you at the Lucky Lab on July 25th?
Colin
BobD - 1978 Bus . . . . . . . . . . . 111,155 miles
Chloe - 1970 bus . . . . . . . . . . . 206,820 miles
Naranja - 1977 Westfalia . . . . . 108,000 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 1991 Lexus LS400 . . . 78,885 miles

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